Explore that joins a table with max measure

[cristian2]

Hi all!
I have two tables: 1) Customer and 2) Customer phone numbers. Each customer may have many numbers but only one is active at a time. In SQL I just do a subquery on the phones effective_from field with a max to find the latest one. Something like this:

SELECT
  CUST.CUSTOMER_NAME
  CUST_NO.TEL

  FROM "DEMO"."CUSTOMER" CUST
  left join "DEMO"."CUST_TEL" CUST_NO

  WHERE CUST.CUSTOMER_PK = CUST_NO.CUSTOMER_PK
  AND CUST_NO.EFFECTIVE_FROM =
  (
  SELECT MAX(CUST_NO_2.EFFECTIVE_FROM)
  FROM "DEMO"."CUST_TEL" CUST_NO_2
  WHERE CUST.CUSTOMER_PK  = CUST_NO_2.CUSTOMER_PK
  )

I do this in a derived table now and it works fine but I wonder how I can do this using LookML?
Any ideas?
I did a max measure in the view for CUST_TEL and now I want to join this view into my CUST view in an explore.

Cheers,
c